Internal combustion (IC) engines typically include exhaust systems designed to collect, route, and discharge the engine's exhaust gases. An exhaust system commonly includes piping to guide exhaust gases away from the engine. Exhaust systems of modern IC engines also include various exhaust after-treatment (AT) devices, such as a gasoline three-way catalytic converter, a diesel oxidation catalytic converter, and other devices, to effectively convert toxic byproducts of combustion to less toxic substances by way of catalyzed chemical reactions.
A typical AT device employs a catalyst monolith selected or formulated to achieve effective performance at exhaust gas temperatures of the specific IC engine equipped therewith. Such an AT device is, however, less efficient under engine cold-start conditions and until the subject AT device achieves light-off, i.e., reaches its effective operating temperature. Accordingly, an IC engine equipped with such an AT device will generally produce elevated exhaust emissions following an engine cold-start and until the AT device light-off.